NiWC Hardfacing by Gas Metal Arc Welding GMAWCSC was used to widen the operation window, 3D printing approach to select weaving pattern, advanced EPMA to analyze microstructure, Introduction SUPPLEMENT TO THE WELDING JOURNAL, DECEMBER 2016 Sponsored by the American Welding Society and the Welding Research Council and thermodynamics to show WC loss Cladding the surface of a steel substrate with a layer of nickel (Ni) alloy embedded with hard tungsten carbide (WC) particles can significantly improve the wear and corrosion resistance of the steel. Various processes BY P. YU, X. CHAI, D. LANDWEHR, AND S. KOU have been used for hardfacing with Ni- WC, for instance, plasma transferred arc welding (PTAW), submerged arc welding (SAW), laser beam welding (LBW) and cladding, and gas metal arc welding (GMAW) (Ref. 1). The PTAW process is the most common and efficient method for shop production, but it is impractical for field welding applications (Ref. 2). Gas metal arc welding is a low-cost alternative to PTAW and LBW. It is suitable for cladding over small areas that need protection by hardfacing, cladding small internal diameters, or repairing small damaged areas in existing cladding. Choi et al. (Ref. 2) made single-bead WELDING RESEARCH Ni-WC cladding using a Lincoln Electric Power Wave 455M/STT power source for GMAW. The filler metal was 1.6- mm-diameter Arctec Tungcore FCS cored wire. The heat input varied with the filler metal transfer mode: lowest with the short-circuiting mode, higher with the globular mode, and highest with the spray mode. It was shown that increasing the heat input increased both dilution and carbide dissolution. Vespa et al. (Ref. 3) made single-bead Ni-WC cladding using a Jetline Engineering process controller called CSC-MIG along with a Miller Electric XMT 350 CC/CV power source. The filler metal was a 1.6-mm PolyTung NiBWC cored electrode wire manufactured by Polymet Corp. It was also reported that increasing the heat input increased WC dissolution. In general, the microstructure of Ni-WC cladding made by various processes consists of “chunks of unmelted tungsten carbide in a nickelbase alloy matrix,” according to ISO/TR Technical Report 13393 (Ref. 4). The microstructure of Ni-WC cladding made by GMAW has been discussed by Choi et al. (Ref. 2) and Vespa et al. (Ref. 3), which will be mentioned subsequently in the present study. The cladding of Ni-WC has exceptional abrasion resistance and moderate corrosion resistance (Ref. 4). However, increasing the heat input can increase the dissolution of tungsten carbide particles and reduce the abrasion resistance. It also increases the dilu DECEMBER 2016 / WELDING JOURNAL 451-s ABSTRACT Nickel cladding reinforced with hard tungsten carbide particles was deposited on steel by both conventional gas metal arc welding (GMAW) and GMAW controlled short circuiting (GMAWCSC). Singlebead hardfacing was deposited at various heat inputs. The current/voltage waveforms were recorded during welding. It was found that the window of welding parameters for making a smooth cladding without much spatter was significantly wider with GMAWCSC than conventional GMAW. While the cladding dilution by steel increased with increasing heat input as expected, the dilution increase was less with GMAWCSC than conventional GMAW. A lowcost 3D printerbased substrate manipulation table was built to move the steel plate under a stationary welding gun for deposition on a designated area on steel. Thus, even when a robot is unavailable to weave the gun over the steel, the effect of the welding gun’s weaving pattern on the resultant cladding can still be examined, e.g., the uniformity of the cladding thickness and the particle distribution in the cladding. A stateoftheart FESEM+EPMA with a very small beam diameter of 80 to 100 nm was used to identify various phases inside both the tungsten carbide particles and the matrix. An eightlayer square cladding was deposited and its overall composition measured. Thermodynamic calculations based on this composition showed that substituting Ni with Cr can degrade the cladding by causing brittle Crcontaining carbide to form at the expense of WC. KEYWORDS • Hardfacing • Cladding • Controlled Short Circuiting • Tungsten Carbide • Nickel P. YU and S. KOU are with the Department of Materials Science and Engineering, University of Wisconsin, Madison, Wis. X. CHAI is with Novelis Global Research & Technology Center, Kennesaw, Ga. D. LANDWEHR is with Fisher Barton Technology Center, Watertown, Wis.
Welding Journal | December 2016
To see the actual publication please follow the link above